a) Field of the Invention
The present invention pertains to a device and a method for correcting a flexible material web that is guided to a processing machine, wherein the underside of the material web incorrectly points upward due to wrongly connected web ends or due to twisting, and wherein the material web is turned at least once about its longitudinal axis in such a way that the underside of the material web once again correctly points downward and the correct upper side of the material web is transported to the processing machine.
b) Description of the Related Art
Half-finished materials in the form of strips are increasingly utilized, in particular, in the hygiene industry. The material webs have a width between approximately 25 mm and 200 mm. The material webs usually consist of bonded webs, foils, papers, airlaids or composites of the aforementioned materials. These material webs have a significant thickness between approximately 0.5 mm and 5 mm and consequently can only be wound up into a roll conditionally. This led to the development of a packaging concept, according to which the material web is either placed on a pallet or into a cardboard box in layers in a zigzag-like fashion or precut and plaited into a rectangular stack consisting of individual webs that lie parallel to one another. According to the pertinent terminology, this technique is also referred to as “festooning.” Drawings of corresponding stacks can be found, for example, in DE 101 25 452 A1 or publication EP 091 0542 B1. The ends of the individual parallel or zigzag-shaped material webs are connected to one another, for example, by means of bonding or sewing in order to allow a largely continuous supply to the processing machine and to minimize downtimes. The processing machines may consist, for example, of machines for manufacturing panty liners, sanitary napkins or baby diapers.
During the removal of the material web from the festooned pack, the high supply and removal speeds on the order of approximately 300 m/min cause the material web to oscillate and vibrate and, as a consequence thereof, lead to a rotation of the material web that is also referred to as a “twist” according to the pertinent terminology. Another problem arises if the ends of the material webs were wrongly connected to one another and the upper side of the material web that should be provided, for example, with an impregnation in the processing machine points downward. The twists and the wrongly connected ends of the material web ultimately lead to a non-functional end product due to the inverted upper side and underside of the material web. Twists can also lead to tearing of the material web. This also results in the downtimes of the processing machine and the accumulation of costly waste of a high-quality and expensive half-finished material.
Only a manual correction of twists or wrongly connected material ends is known from the state of the art. This manual correction is very limited and ultimately associated with downtimes of the processing machine. The twist is corrected by turning the material web about its longitudinal axis, namely in the opposite direction, and ultimately controlling that the undesirable twist continues to the free end of the material web. Alternately, an intentional twisting is carried out in order to introduce the correct upper side of the material web into the processing machine. This also is also associated with downtimes of the processing machines and with a significant expenditure of labor.
The pertinent state of the art—U.S. Pat. Nos. 4,212,422, 2,821,387, DE 2 137 706 B2—pertains to, for example, devices and methods in which deflection rolls are supported in a pivoted fashion and the twist of the web is corrected by adapting the cylinder position to the degree of twisting. The defect of the supplied web is limited to deviations in the directional transport in the state of the art. In addition, only a flexible reaction of deflection rolls that are supported in a pivoted fashion to a supply sensor takes place in this case rather than an untwisting of the web.